System and method for detecting optical probe connection

ABSTRACT

A catheter system includes an electronic console; a catheter having a proximal end attachable to the console and a distal end configured to house therein an optical probe; an optical fiber configured to transmit from the console to the optical probe excitation radiation of a first wavelength, and configured to return to the console an optical response signal having a second wavelength longer than the first wavelength; a detector configured to detect intensity of the optical response signal; and a processor configured to determine, based on the detected intensity of the optical response signal, whether the catheter is properly connected to the console. The optical response signal is generated within the optical fiber itself in response to transmitting the excitation radiation therethrough. The optical response signal is an auto-fluorescence signal and/or Raman scattering signal generated from the optical fiber itself.

CROSS-REFERENCE TO RELATED APPLICATIONS

n/a

BACKGROUND

Field

Disclosure of present application relates generally to optical imaging,and in particular it relates to systems and methods for evaluatingoptical connection of fiber-based endoscopes or catheters to a console.The optical connection is evaluated using fiber-based Raman scatteringor fluorescence signals such as spectra and intensity.

Related Art

Fiber optics-based probes, such as catheters and endoscopes, have beendeveloped to access and image internal organs of humans and animals, andare now commonly used in various medical fields. For example incardiology, optical coherence tomography (OCT), white lightback-reflection, near infrared spectroscopy (NIRS) and fluorescenceoptical probes have been developed to obtain structural and/or molecularimages of vessels and other bodily lumens with a catheter. An OCTcatheter, which generally comprises a sheath, a coil and an opticalprobe, is navigated through a lumen, by manual or automatic control. Incardiology, the catheter is navigated to a coronary artery.

OCT and other fiber-based catheters are typically attachable to aconsole via a patient unit interface (PIU) so the catheter needs to bemechanically connected in a secure manner. In addition to a mechanicalconnection, the optical probe of the catheter needs to engage and alignwith other optical elements in the PIU to ensure proper transmission oflight between the console and catheter. Therefore, evaluating theoptical probe connection to the console is highly desirable in order torecognize the connection status thereof before using the catheter in apatient. In this manner, when an unexpected misalignment ordisconnection occurs, the console system is able to alert medicalpersonnel of potential errors.

Conventional techniques for evaluating the connection of an opticalprobe typically include interferometry methods such as OFDR (OpticalFrequency Domain Reflectometry) or return power loss analysis. OFDR iscommonly used to detect fiber connections, insertion losses, fiberdamages, etc., in the field of telecommunications (see, e.g., U.S. Pat.Nos. 6,009,220 and 5,625,450). Return power loss refers to a techniqueof measuring losses from the distal optical probe for evaluating fiberconnections for spectroscopic catheter (see. e.g., U.S. Pat. No.7,132,645). Other techniques for evaluating an endoscope's status priorto its use on a patient include the use of dedicated test equipment todetermine if an endoscope is ready for use (U.S. Pat. No. 8,758,223) andperformance of optical tests compared to previously established databaseof threshold values (U.S. Pat. No. 6,069,691).

In the interferometry methods, the catheter sheath and/or the distal endof the optical probe need to be detected to confirm the connections.However, each optical probe has different length so the frequency of theinterferometer varies. In some cases, the detection fails due to out ofsystem frequency range. To accommodate various types of catheter orendoscopes, the system becomes complicated to increase the frequencyrange. Also, objects placed near the catheter sheath affect theinterferometry analysis due to bending or interference, which results ina loss of reliability of detections. In return power detection methods,back-reflection power at different interface stages is evaluated, butreflections are very weak or may undergo transmission loss (attenuation)so it is difficult to reliably detect optical probe connections.Further, the use of dedicated test equipment increases the cost and timenecessary to evaluate the connection status of an endoscope. Moreover,comparing optical tests of an instrument to previously establishedthresholds limits the evaluation to only the values of previouslyestablished thresholds which are unique to each type or model ofendoscope.

SUMMARY

The present patent application aims to improve on the above-describedstate of the art. According to an aspect of the present application, asystem is able to evaluate the status of optical probe connections of acatheter or endoscope by detecting Raman scattering and/orauto-fluorescence signals from the optical probe itself. Sinceevaluation of connection is performed using Raman scattering and/orauto-fluorescence signals of the optical probe itself, the methoddisclosed herein is able to achieve reliable detection of optical probeconnection even before the catheter is inserted in the patient. Inaddition, since Raman scattering and/or auto-fluorescence signals areobtained from the optical probe itself, the optical probe connection canbe accurately evaluated regardless of the type or model of catheter orendoscope.

According to one aspect of the present invention, a catheter systemincludes an electronic console; a catheter having a proximal endattachable to the console and a distal end configured to house thereinan optical probe; an optical fiber configured to transmit from theconsole to the optical probe excitation radiation of a first wavelength,and configured to return to the console an optical response signalhaving a second wavelength longer than the first wavelength; a detectorconfigured to detect intensity of the optical response signal; and aprocessor configured to determine, based on the detected intensity ofthe optical response signal, whether the optical probe is properlyconnected to the console, wherein the optical response signal isgenerated by at least one of photon scattering and auto-fluorescencewithin the optical fiber itself in response to transmitting theexcitation radiation therethrough.

According to another aspect, a method of determining optical connectionof a catheter to an electronic console is disclosed. The catheter has aproximal end attachable to the console, a distal end configured to housetherein an optical probe, and an optical fiber that extends from thedistal end to the optical probe. The method comprises: connecting theproximal end of the catheter to the console; transmitting excitationradiation from an optical source to the optical probe through theoptical fiber, and collecting an optical response signal having awavelength longer than that of excitation radiation; detecting theintensity or wavelength of the optical response signal; and determining,based on the detected intensity or wavelength, whether the optical probeof the catheter is properly connected to the console. The opticalresponse signal is generated by at least one of photon scattering andauto-fluorescence within the optical fiber itself in response totransmitting the excitation radiation therethrough.

According to a further aspect of the present invention, a multimodalitysystem includes first and second modalities, a catheter, and aprocessor. According to a further aspect of the present invention, amultimodality system includes first and second modalities, a catheter,and a processor. The catheter has a proximal end attachable to aconsole, a distal end configured to house therein an optical probe, andan optical fiber that extends from the distal end to the optical probe.The catheter is configured to transmit therethrough first radiation fromthe first modality and second radiation from the second modality toirradiate a sample. In response to transmitting the first and/or secondradiations therethrough, the optical fiber generates an optical signalresponse in the form of Raman scattering and/or a fluorescence signalgenerated within the optical fiber itself. One or more detectors areconfigured to detect the intensity or wavelength of the optical signalresponse generated by the fiber itself. The one or more detectors arealso configured to detect interference patterns based on collectedscattered light emitted from a region of interest of the sample inresponse to irradiating the sample with the first radiation of the firstmodality, and detect fluorescence intensity based on fluorescent lightemitted from the region of interest in response to irradiating thesample with the second radiation of the second modality. The processoris configured to process the interference patterns and detectedfluorescence intensity emitted from the sample to generate one or moreimages of the region of interest. The processor is further configured todetermine, based on the detected intensity or wavelength of the opticalresponse signal, whether the optical probe is properly connected to theconsole. In particular, in response to determining an status ofconnection of the optical probe to the console, the processor isconfigured to inform a user of the connection status to prevent unsafeirradiation or to ensure safe irradiation of the sample with the firstradiation from the first modality and/or with the second radiation fromthe second modality. In one embodiment, the first modality is an OCTsystem and the second modality is a fluorescence subsystem.

Further features and advantageous effects of the invention will becomeapparent to those skilled in the art from the following description ofexemplary embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an exemplary multimodality catheter system forimaging coronary arteries or other bodily lumens.

FIG. 2A schematically shows one exemplary implementation of relevantparts of a patient interface unit (PIU). FIG. 2B shows an exemplaryimplementation of free-space optics used as a one-to-one opticalconnection in a fiber optic rotary joint (FORJ).

FIG. 3A illustrates a free space beam combiner as an exemplaryimplementation of free-space optics used for multi-modality opticalconnections in the fiber optic rotary joint (FORJ). FIG. 3B illustratesan exemplary implementation of a fiber collimator unit.

FIG. 4A illustrates an example of an optical probe arranged at thedistal end of the catheter with exemplary light rays incident on asample. FIG. 4B shows exemplary movement of the distal end of thecatheter with respect to the sample and exemplary light rays scatteredby the sample and collected by the optical probe.

FIGS. 5A through 5C graphically illustrate a comparative example ofassessing optical probe connection based on detected OCT signals. FIG.5D illustrates a graph of exemplary spectra of excitation laser light,and Raman and/or auto fluorescence signal obtained from the opticalprobe fiber itself. FIG. 5E illustrates an exemplary graph of indicativeof optical probe connection status as a function of detected Ramanand/or auto fluorescence signal intensity being compared to a thresholdlevel.

FIG. 6A shows a graph of spectra of fiber background and tissue signalsobtained when irradiating a sample with excitation light using theoptical probe of the catheter. FIG. 6B is a graph showing spectra oftissue signals after removing the fiber background signal.

FIG. 7A shows a graph of Signal-to-Noise Ratio (SNR) calculation resultsfrom measured fiber background and a tissue signal. FIG. 7B shows agraph of auto-fluorescence intensity levels detected from Raman and/orauto fluorescence signals obtained from the fiber of the optical probe.

FIG. 8A illustrates an exemplary implementation of an electronic consoleconnected to the multimodality catheter. FIG. 8B is a block diagram ofan exemplary computer control system for performing control and imageprocessing in the multimodality catheter system.

FIG. 9 illustrates an exemplary flow process for controlling themultimodality system to perform optical probe connection detection andimage generation.

FIG. 10A shows a cross-sectional view of an exemplary fiber bundle, andFIG. 10B show the cross-section of an exemplary multi-fiber structure,which are examples of fiber optics arrangements for the multi-modalitycatheter system.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanyingdrawings which are illustrations of exemplary embodiments in which thedisclosed invention may be implemented and practiced. It is to beunderstood, however, that those skilled in the art may develop otherstructural and functional modifications without departing from thenovelty and scope of the instant disclosure.

In referring to the description, specific details are set forth in orderto provide a thorough understanding of the embodiments disclosed. Someaspects of the present disclosure may be implemented by a computersystem that includes, in general, one or a plurality of processors forprocessing data including instructions, random access (volatile) memory(RAM) for storing data and instructions or programs, read-only(non-volatile) memory (ROM) for storing static information andinstructions, a data storage devices such as a magnetic or optical diskand disk drive for storing information and instructions, an optionaluser output device such as a display device (e.g., a LCD or OLEDmonitor) for displaying information to a user, an optional user inputdevice including alphanumeric and function keys (e.g., a keyboard ortouchscreen) for communicating information and command selections to theprocessor, and an optional user input device such as a pointing device(e.g., a mouse) for communicating user input information and commandselections to the processor.

In the present application, the described embodiments may be implementedas an apparatus, a method, or non-transitory computer-readable mediumproduct storing thereon one or more programs. Accordingly, someimplementations may take the form of an entirely hardware embodiment, anentirely software embodiment (including firmware, resident software,micro-code, etc.), or an embodiment combining software and hardwareaspects that may all generally be referred herein as a “module”, a“unit”, or a “system”. Some embodiments described below with referenceto flowchart illustrations and/or block diagrams may be implemented bycomputer-executable programed instructions. The computer programinstructions may be stored in computer-readable media that when executedby a computer or other programmable data processing apparatus causes thecomputer or processing apparatus or processor to function in aparticular manner, such that the instructions stored in thecomputer-readable media constitute an article of manufacture includinginstructions and processes which implement the function/act/stepspecified in the flowchart and/or block diagram.

The terms first, second, third, etc. may be used herein to describevarious elements, components, regions, parts and/or sections. It shouldbe understood that these elements, components, regions, parts and/orsections are not limited by these terms of designation. These terms ofdesignation have been used only to distinguish one element, component,region, part, or section from another region, part, or section. Thus, afirst element, component, region, part, or section discussed below couldbe termed a second element, component, region, part, or section merelyfor purposes of distinction but without limitation and without departingfrom structural or functional meaning.

As used herein, the singular forms “a”, “an”, and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It should be further understood that the terms “includes”and/or “including”, “comprises” and/or “comprising”, “consists” and/or“consisting” when used in the present specification and claims, specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof not explicitly stated. Further, in thepresent disclosure, the transitional phrase “consisting of” excludes anyelement, step, or component not specified in the claim. It is furthernoted that some claims may be drafted to exclude any optional element;such claims may use exclusive terminology as “solely,” “only” and thelike in connection with the recitation of claim elements, or it may useof a “negative” limitation.

As used herein the term “endoscope” refers to a rigid or flexiblemedical instrument which uses light guided by an optical probe to lookinside a body cavity or organ. A medical procedure, in which anendoscope is inserted through a natural opening, is called an endoscopy.Specialized endoscopes are generally named for how or where theendoscope is intended to be used, such as in the mouth during abronchoscopy, or the rectum for a sigmoidoscopy. Other examples includethe cystoscope (bladder), nephroscope (kidney), bronchoscope (bronchi),laryngoscope (larynx), otoscope (ear), arthroscope (joint), laparoscope(abdomen), and gastrointestinal endoscopes. The term “catheter”generally refers to a flexible and thin tubular instrument made ofmedical grade material designed to be inserted through a narrow openinginto a body cavity to perform a broad range of medical functions. Themore specific term “optical catheter” refers to a medical instrumentcomprising an elongated bundle of one or more flexible light conductingfibers disposed inside a protective sheath made of medical gradematerial and having an optical imaging function. A particular example ofan optical catheter is fiber optic catheter which comprises a sheath, acoil, a protector and an optical probe.

In the present disclosure, the terms “optical fiber”, “fiber optic”, orsimply “fiber” refers to an elongated, flexible, light conductingconduit capable of conducting light from one end to another due to theeffect known as total internal reflection. The term “fiber” may refer toone or more light conducting fibers. A fiber has a transparent,homogenous core, where the light is guided, and the core is surroundedby a homogenous cladding. The refraction index of the core is largerthan the refraction index of the cladding. Depending on design choicesome fibers can have multiple claddings surrounding the core.

As used herein the term “optical coherence tomography” or its acronym“OCT” refers to an interferometric, optical tomographic imagingtechnique offering millimeter penetration (approximately 2-3 mm intissue) with micrometer-scale axial and lateral resolution. The term“Raman spectroscopy” refers to an optical technique that reveals thespecific molecular content of a sample by collecting inelasticallyscattered light based on the principles of Raman scattering. As photonspropagate through a medium, they undergo both absorptive and scatteringevents. In absorption, the energy of the photons is completelytransferred to the material, allowing either heat transfer (internalconversion) or re-emission phenomena such as fluorescence andphosphorescence to occur. Scattering is normally an inelastic process,in which the incident photons retain their energy. In Raman scattering,the photons either donate or acquire energy from the medium, on amolecular level. In contrast to fluorescence, where the energy transfersare on the order of the electronic bandgaps, the energy transfersassociated with Raman scattering are on the order of the vibrationalmodes of the molecule. These vibrational modes are molecularly specific,giving every molecule a unique Raman spectral signature. Raman spectraare plotted as a function of frequency shift (1/λ) in units ofwavenumber (cm⁻¹). Fluorescence relates to substances which absorb lightat one wavelength, undergo internal conversion, and then re-emit lightat a longer wavelength as a result of electronic transitions. As anexample, a “highlighter” felt-tip marker appears to “glow” green as itabsorbs blue and ultraviolet light then emits it as green. Fluorescenceprovides a powerful technique for chemical monitoring.

Exemplary embodiments are described below in more detail with referenceto the several drawings where like reference numerals refer to likeparts.

<Multi-Modality Catheter System>

According to a first embodiment, a multi-modality catheter systemincludes an OCT system and a fluorescence subsystem which share a commonoptical probe to illuminate and collect light from a sample. Thecatheter comprises a sheath, a coil, a protector and an optical probe.The optical probe comprises an optical fiber connector, an optical fiberand a distal optics assembly. The OCT system comprises an interferometerand the catheter arranged on the sample arm of the interferometer. Thecatheter having the optical probe, which includes a focusing element(GRIN or ball lens) attached at the distal end of an optical fiber withat least 2 dads (also known as double clad fiber or DCF), is attachableand detachable from the sample arm. The fluorescence subsystem comprisesthe same catheter and an excitation light source separate from theinterferometer.

<OCT System>

More specifically, FIG. 1 illustrates an exemplary multi-modalitycatheter system 100 including an interferometric OCT modality and afluorescence spectroscopy modality that can be applied as anintravascular OCT/fluorescence catheter system for imaging of coronaryor carotid arteries. Alternatively, the multi-modality system 100 can beapplied as an endoscopic system (endoscope) for imaging other bodilylumens. As depicted in FIG. 1, the system 100 includes an OCT modalitycomprised of an interferometer having a sample arm (SAMPLE ARM) and areference arm (REFERENCE ARM), an OCT light source 110 (first lightsource), a detector unit 120, a data acquisition unit 130, and acomputer 190. The sample arm of the interferometer includes a patientinterface unit (PIU) 150 connected to a catheter 160 via a catheterconnector 180. The reference arm includes a reflector 140. Theinterferometer can be of any interferometer configuration, including aMichelson interferometer implemented with optical fibers. In addition,the system 100 includes a fluorescence subsystem (fluorescence modality)comprised of an excitation light source 810 (second light source) alsoconnected to the same catheter 160 via an optical fiber 811, andconnected to computer 190 via the PIU 150. In one embodiment, the system100 uses a swept-source laser (wavelength 1310 nm+/−50 nm) as the OCTlight source 110, and a HeNe laser (wavelength 633 nm) as the excitationlight source 810 for the fluorescence subsystem.

The catheter 160 comprises a sheath, a coil, a tubular protector, and anoptical fiber 107 extending from a proximal end to a distal end along anaxis thereof. In one embodiment, the fiber 107 is double clad fiber(DCF). At the proximal end, the catheter is configured to be detachablyconnected to the PIU 150 via the catheter connector 180, and the distalend of the catheter 160 is configured to house therein a distal opticsassembly (an optical probe) which includes, for example, a ball lensattached at the distal end of the fiber. The distal optics assembly(optical probe) may alternatively include combination of a graded index(GRIN) lens and a refractive element (e.g., grating) attached at thedistal end of the fiber 107. In a further alternative embodiment, theoptical probe may be formed by polishing the distal end of the opticalfiber 107 at a predetermined angle and forming thereon a refractiveelement (grating) by nanoimprint lithography techniques, as described inpublication US 2016/0349417. The optical probe can be configured forside-view imaging or for front-view imaging depending on design choiceand optical/mechanical constraints of the desired application.

In operation, light from the light source 110 is guided through thesample arm to a sample 170, and through the reference arm to thereflector 140. Light retuning from the sample 170 and reflector 140undergo interference at a beam combiner 104 to thereby generate OCTinterference patterns. Specifically, light from the light source no isdivided by a splitter 102 (fiber splitter or beam splitter) into asample beam and a reference beam which are respectively guided to thesample arm and the reference arm via respective optical fibers (notlabeled). In the sample arm, the sample beam enters a circulator 105,passes to a fiber 106 (e.g., a single mode fiber), and thenceforth thesample beam is delivered to the catheter 160 via the PIU 150. Thecatheter 160 is connected at its proximal end thereof to the PIU 150 viathe connector 180, and the PIU 150 is also connected to computer 190.Under control of computer 190, the PIU 150 directs the sample beam toirradiate the sample 170 in a scanning manner. Light of the sample beamreflected and/or scattered by the sample 170 is collected by the distaloptics assembly (optical probe) arranged at the distal end of thecatheter 160, and the collected light is transmitted back to the PIU 150through either the same fiber 107 or other collection fibers (notshown). From the PIU 150, the collected light is guided by fiber 106back to the circulator 105. In turn, a beam combiner arranged in the PIU150 forwards the collected light to the circulator 105 which then guidesthe collected light of the sample beam to the combiner 104.

At the same time, in the reference arm, light of the reference beamenters a circulator 103 and is delivered to the reflector 140 via anon-labeled optical fiber. In the case of Time Domain OCT (TD OCT)imaging, the reflector 140 may be implemented as a scanning mirror. And,in the case of Frequency Domain OCT (FD-OCT) imaging, the reflector 140may be implemented as a stationary mirror. Light of the reference beamreflected from the reflector 140 passes through the circulator 103, andis also guided by the circulator 103 to the combiner 104. In thismanner, the sample and reference beams are combined at the combiner 104and interference patters formed by the sample and reference beams aredetected by one or more first detectors 121 (OCT detectors) to generateinterference signals according to OCT principles.

Here, it is noted that a fiber optic circulator (e.g., circulator 103 or105 in FIG. 1) is a passive, polarization-independent, three-port devicethat acts as a signal router. Light from a first fiber is input to thecirculator via a first port and directed to a second fiber via a secondport. Light returning through the second fiber is redirected to a thirdfiber via a third port with virtually no losses. That is, light inputinto the first port is not directly coupled into the third port fiber,and light input into the second port is not coupled at all into thefirst port fiber. Therefore, the optical circulator (103 and 105)enables a balanced output of the sample and reference beams to obtainaccurate interference patterns from the OCT interferometer. However,other equivalent optical arrangements (e.g., combination of mirrors andbeam splitters) can be used instead of optical circulators.

The output of the interferometer (interference patterns) is detected bythe detector 121 (first detector). The first detector 121 can beimplemented by multiple photodiodes (e.g., an array of photodiodes), aphoto multiplier tube (PMT), a multi-array of cameras or other similarinterference pattern detecting device. The signals output from the firstdetector 121 are pre-processed by a first data acquisition electronicscard (DAQ1) 131. The DAQ1 digitizes the OCT signals and transfers theOCT data to computer 190. It is noted that data acquisition (DAQ) moregenerally refers to the process of measuring an electrical or physicalsignal such as voltage, current, temperature, pressure, or sound with acomputer. A DAQ system may include sensors, measurement hardware, andexecutable software. In the present disclosure a DAQ unit (module orsystem) refers to the hardware and/or software necessary to measure thesignals from the OCT system and fluorescence subsystem with computer190. In this manner, computer 190 performs signal processing of the OCTsignals output from detector 121 to generate OCT images. Interferencepatterns formed by interference of the sample and reference beams aregenerated only when the path length of the sample arm matches the pathlength of the reference arm within the coherence length of the lightsource 110.

<Fluorescence Subsystem>

In the fluorescence modality (fluorescence subsystem), the excitationlight source 810 (second light source) emits excitation light with awavelength of 633 nm. The excitation light is guided first to the PIU150 through a fiber 811, and the beam combiner in PIU 150 transmits theexcitation light to the distal optics of catheter 160 via the fiber 107.In this manner, the catheter 160 also irradiates the sample 170 withexcitation light having a wavelength different from that of the OCTlight. The sample 170 emits auto-fluorescence (NIRAF signal) orfluorescence (NIRF signal) with broadband wavelengths of about 633 to900 nm, in response to being irradiated by the excitation light. Theauto-fluorescence (or fluorescence) light is collected by the distaloptics of the catheter 160 and delivered to a fluorescence detector 122(DET2) via an optical fiber 108 which is connected to the PIU 150. Thefluorescence signal (fluorescence intensity signal) output from detector122 is digitized by a data acquisition electronics card 132 (DAQ2), andthe digitized fluorescence data is transmitted to computer 190 for imageprocessing.

The multi-modality catheter system 100 is illustrated in FIG. 1 as beingconstituted of separate elements for ease of illustration. However, aconsole containing the different elements (e.g., interferometer, PIU,computer, etc.) and having connection ports for electrically couplingmedical instruments such as a catheter is generally used when performinga medical procedure. An example of a console having connection ports forelectrically coupling equipment thereto for performing a medicalprocedure is described in publication US 20170333013.

<Patient Unit Interface (PIU)>

FIG. 2A schematically shows one exemplary implementation of relevantparts of a patient interface unit (PIU) 150 which is detachablyconnected to the proximal end of catheter 160 (shown in FIG. 1). Asshown in FIG. 2A, the PIU 150 is encased in an outer housing 202, whichserves as a housing for mechanical, electronic, and optical componentsuseful for control of the optical probe of catheter 160. Included in thehousing 202 of PIU 150 is a fiber optic rotary joint (FORJ) comprised ofa free-space optical connector 210, a rotational motor 220, a motorizedtranslation stage 214. At one end, the PIU 150 is provided with anoptical/electrical connector 216, and at the other end thereof the PIU150 is provided with a catheter connector 218. The connector 216 servesto connect one or more fibers 206 a encased in a protective jacket 204 aand electronic wiring connections 215 of the PIU 150 to an operatingconsole which includes the computer 190. The console connects to the PIUvia a cable bundle. A first end of a double clad fiber (DCF) 206 bencased in a protective jacket 204 b are part of the free-spaceconnector 210 and the other end of DCF 206 b is connected to thecatheter 160 via the connector 218.

The motor 220 and motorized translation stage 214 provide rotational andtranslational torque for actuation of the movable components of catheter160. Motor 220 drives a non-labeled shaft to rotate a first gear 212which transfers rotational torque to a second gear 211. The motor 220 ismechanically fixed to a base plate 513. In addition, a motorizedtranslation stage 214 is also fixed to the base plate 213. The motorizedtranslation stage 214 serves to provide translational torque forcontrolling linear movement (insertion into a lumen or pullback) of themovable components within catheter 160. A support beam 208 providessupport and directional control for translational movement of themovable components within catheter 160. In other words, support beam 208serves as a linear guide for translational movement. The motorizedtranslation stage 214 is also used for providing translational torqueduring a pullback operation. The connector 518 is a catheter connectorto be mechanically attachable to and detachable from the catheter 160.Although a single fiber 206 a and a single DCF 206 b are shown in FIG.2A, more than one fiber can be used to transmit the light from OCT lightsource 110 and light from the excitation light source 810 to the PIU150.

FIG. 2B shows a simplified view of an exemplary implementation of thefree-space optical connector 210 which is part of the FORJ. Thefree-space optical connector 210 includes free space optics such as apair of lenses 2101 and 2102. The FORJ allows uninterrupted transmissionof optical radiation from one or both of the light sources (110 and 810)to the catheter 160 while rotating the double clad fiber 206 b on therotor side (right side). The FORJ has a free space optical beam couplerto separate rotor and stator sides. The rotor and stator sides eachincludes at least a fiber and a lens to ensure the light is transmittedas a collimated beam. The rotor side is connected to the catheter 160,and the stator side is connected to the optical sub-systems within thePIU 150. The rotational motor 220 delivers the rotational torque to therotor or rotational side. It should be understood from FIG. 2B that thelens 2101 needs not be separated from the fiber 206 a, and similarlylens 2102 needs not be separated from the fiber 206 b. As long as acollimated beam is transferred from the stator side to the rotor sideand vice versa, the lenses 2101 and 2102 can be arranged at any positionbetween fiber 206 a and fiber 206 b. Indeed, for ease and convenience offabrication, the lenses 2101 and 2102 can be fused or glued with epoxyor resin at the respective tips of fiber 206 a and fiber 206 b.

<Free-space Beam Combiner>

FIG. 3A illustrates an exemplary embodiment of a free-space beamcombiner 300 which can be implemented within the free-space opticalconnector 210. The beam combiner 300 shown in FIG. 3A is a more detailedrepresentation of the free-space optical connector 210 shown in FIG. 2B.The free-space beam combiner 300 serves to separate the rotor side fromthe stator side of the FORJ. The rotor side is connected to the opticalprobe through catheter connector 218 (shown in FIG. 2A), and the statorside is connected to the optical sub-systems.

In FIG. 3A, the free-space beam combiner 300 includes a plurality offiber collimator units, which function as an OCT light channel 302, areturn optical signal channel 304, an excitation light channel 306, onthe stator side, and an optical probe channel 308, on the rotor side.The free-space beam combiner 300 also includes a plurality of dichroicbeam splitters (dichroic filters) 310A and 310B, one or more mirrors312, and one or more optical filters 320. As shown in FIG. 3A, the OCTchannel 302 transmits OCT light in both directions (illumination andcollection). The excitation light channel 306 transmits excitation lightin only one direction (from the console to the optical probe). Theoptical probe channel 308 transmits OCT light and excitation light tothe optical probe (and through the catheter to the sample); the opticalprobe channel 308 also serves to transmit light from the optical probeback to the detectors. And, in turn, the return optical signal channel304 transmits a response signal returned from the optical probe channeltowards the console.

OCT light from the OCT light source 110 travels through OCT channel 302,dichroic mirror 310A, and optical probe channel 308 to irradiate anon-illustrated sample. The excitation light channel 306 transmits lightfrom the excitation light source 810 to the sample. To that end, anexcitation light beam travels through excitation light channel 306, isguided by mirror 312 towards the dichroic beam splitter 310B throughwhich the excitation light travels uninterrupted to be redirected bydichroic 310A towards the optical probe channel 308. As explained inmore detail elsewhere in this specification, the excitation lighttransmitted through the optical probe channel 308 causes the opticalprobe to generate a response optical signal in the form ofauto-fluorescence and/or Raman scattering. The dichroic beam splitters310A and 310B serve to separate and guide the lights of differentwavelengths including OCT light, excitation light, and a return opticalsignal (Raman scattering and auto-fluorescence) generated by the probeitself. The one or more optical filters 320, which can be low-passfilters or band-pass filters, are arranged in front of the returnoptical signal channel 304 to allow the Raman scattering and/orauto-fluorescence signals coming back from the optical probe to traveltherethrough and to prevent the excitation light from returning todetector because of the need to minimize excitation light noises at thefluorescence detector. The cut-off wavelength of the optical filter 320(low-pass or band-pass) is selected from around 645 to 700 nm.

<Optical Probe Connection>

As shown in FIG. 3A, one end of the fiber collimator unit of channel 308connects to (and is part of) the free-space beam combiner 300 and theother end (second end) of the collimator unit connects to the opticalprobe. Since the optical probe comprises a fiber connector at theproximal end thereof, and that fiber connector of the probe is connectedto the fiber collimator unit of channel 308, it is important to confirmthe optical alignment of the fiber collimator unit of channel 308 withthe fiber connector of the optical probe. Most fiber optic connectorsare plugs or so-called male connectors with a protruding ferrule thatholds a fiber in the center therein and aligns the fiber for mating twofibers or for connecting the fiber to a light source or detector. Fiberconnectors usually use a mating adapter portion to mate two connectorferrules, where the mating adapter fits a securing mechanism of theconnectors (bayonet, screw-on or snap-in) to lock the connectedportions. The ferrule design can be made specific for connecting to amating adapter or for connecting directly to light sources like LEDs andVCSELs, or to detectors like PIN photodiodes. In the field of medicalimaging with fiber-optic based catheters, the design of optical catheterconnectors must meet the requirements of sterile usage, reliableperformance, ease of assembly, and intuitive connection anddisconnection procedures. To that end, the catheter connector shouldprovide a clear indication that proper engagement between the catheterconnector and the PIU is achieved.

In the present application, as shown in FIG. 1, a catheter connector 180connects the fiber 107 of catheter 160 to the PIU 150. In FIG. 3A, arotatable fiber collimator unit 380 for the optical probe channel 308 isconfigured to engage and disengage with fiber 107 of catheter 160. FIG.3B shows the fiber collimator unit 380 in more detail. The fibercollimator unit 380 includes a sleeve 382 and a ferrule 384. The ferrule384 holds in the center thereof a core 1071 of fiber 107. The fibercollimator unit 380 connects and aligns on one side the fiber 107 and onthe other side a lens 381 so that light is transmitted reliably from thestator to the rotor and vice versa. The lens 381 is attached to thesleeve 382 by an adhesive material 385, such as epoxy or resin material.The fiber collimator unit 380 may be implemented as a bayonet styleconnector requiring rotation of the connector about the axis of theoptic fiber 107 to engage the optical probe. Alternatively, a fiberconnector may be implemented at the second end the fiber collimator unit380 as a latching connector, a plug-to-jack connector, a snap-inconnector, and the like. In this manner, the fiber connector at thesecond end of fiber collimator unit 380 serves to engage and disengagewith the fiber connector of catheter 160. The fiber collimator unitscorresponding to channels 302, 304 and 306 have a similar structure tothe fiber collimator unit 380 except that those fiber collimator unitsare not rotatable.

<Optical Probe>

FIG. 4A illustrates an exemplary representation of a distal end (opticalprobe) of catheter 160. As illustrated in FIG. 4A, catheter 160comprises a transparent sheath 410, a coil 420, a transparent protector430 and an optical probe 450. The optical probe 450 arranged at thedistal end of the catheter 160 includes a double clad fiber 452, a lens454 (e.g., a GRIN lens or a ball lens), and a reflecting and/ordiffracting element (e.g., prism) 456. The catheter 160 is connected atthe proximal end thereof to the PIU 150 (as shown in FIG. 1) via aconnector 180. The coil 420 shown in FIG. 4A delivers rotational torquefrom the proximal end to the distal end of the catheter 160. Asexplained above, the rotational torque is provided by rotational motor220 located in the PIU 150. At the distal end of the catheter 160, areflecting surface or diffracting surface of diffracting element 456(e.g., a mirror, a prism, or a grating) deflects the illumination light(sample beam) in a transverse direction toward the sample (wall of thelumen cavity). As shown in FIG. 4A, the optical probe 450 is configuredfor side-view imaging, where the illumination light incident on thesample surface travels along a line transverse to the catheter's axisOx. Depending on the design of the optical probe, the illumination lightmay also be guided in a direction substantially parallel to thelongitudinal axis Ox for front-view imaging.

The optical probe 450 is rigidly attached to the inner surface of coil420, so that the distal end (tip) of double clad fiber 452 spins(rotates) along with the optical probe 450 to obtain an omnidirectionalview of the inner surface of hollow organs (lumens), such as vesselsbeing imaged. At the proximal end of the optical probe 450, the doubleclad fiber 452 is connected with the PIU 150 via a non-illustrated fiberconnector. The double clad fiber 452 is used to deliver and collect OCTlight through the core, and to collect backscattered and fluorescentlight from the sample through the cladding, as explained more in detailbelow. The lens 454 is used for focusing and collecting light to and/orfrom the sample, by disposing the catheter 160 at a working distance(Wd) from the sample. The intensity of backscattered light transmittedthrough the cladding of double clad fiber 452 is relatively higher thanthe intensity of backscattered light collected through the core becausethe size of the core is much smaller than the cladding.

FIG. 4B illustrates the distal optics of catheter 160 imaging the wallof a lumen cavity (a blood vessel) at variable distances between thecatheter and the sample surface (vessel wall). As illustrated in FIG.4B, fluorescence and backscattered light can be collected at a pluralityof working distances (Wd1, Wd2, Wd3 . . . ). Therefore, the detectedfluorescence intensity can be detected as a function of the distancebetween catheter and the lumen cavity wall (wall of blood vesselsample). That is, the detected intensity of collected fluorescencedecreases with increased distance from catheter to sample (vessel wall).

<Fiber-Based Raman Scattering and Fluorescence Optical Signal Response>

Fiber-optic catheter configurations that combine Raman spectroscopy withoptical coherence tomography (OCT) have been proposed by previous patentapplications and academic publications; see, for example, Motz et al.,“Optical Fiber Probe for Biomedical Raman Spectroscopy”, Applied OpticsVol. 43, No. 3, 20 Jan. 2004, US 2008/0304074 (Brennan), and US2012/0176613 (Marple et al.). In these and other publications, it hasbeen found that the collection of Raman spectra from biological tissue,i.e., Raman spectra in the wavenumber region from about 400 to 2,000cm⁻¹, through optical fibers is complicated by the Raman signal(background signal) from the fiber itself. The intensity of the fiber'sbackground signal is equal to, or even larger than, the Raman scatteringsignal from the tissue being examined. The background signal of thefiber is composed of Raman scattering from the fused-silica core and/orcladding, and fluorescence from impurities and dopants used to producethe fiber core and/or cladding, which are distributed along the entirelength of the fiber (approximately 1-3 meters) typically used in acatheter.

Ma et al., in “Fiber Raman background study and its application insetting up optical fiber Raman probes”, Appl. Opt. 1996, found that (a)all Raman background spectra of fused-silica fibers are very similarregardless of the difference in cladding and buffer materials; and thatthe overall background intensity increases with the fiber numericalaperture but has no obvious relation with the core diameter. Therefore,in catheters that combine Raman spectroscopy with optical coherencetomography, it has been necessary the use of a band-pass filter at thedistal end of the illumination fiber(s) to remove the silica Raman bandsarising from the fiber itself before illuminating a sample, and the useof a long-pass filter disposed before the collection fiber(s) so thatonly the sample-based Raman signal enters the collection fiber(s). Inother words, in order to collect Raman spectra from a sample, it hasbeen conventionally necessary to incorporate complex optics and filterson the distal end of optical catheters. This makes the catheters notonly more complicated to fabricate, but also more expensive and lessflexible.

The inventor herein proposes a fiber-optic based catheter system that isable to evaluate the status of the optical probe connection by detectingRaman and/or auto-fluorescence spectra signals generated from theoptical probe itself. This proposed method is able to achieve reliabledetection of optical probes regardless of the differences in thestructure of the optical probes or the type of catheter being used. Thisis contrary to conventional technology where optical probes aretypically designed with filtering techniques designed to remove themajority of the fiber-based Raman background signal. Referring back toFIGS. 1, 3A and 4A, according to the present invention, detection andevaluation of optical probe connection is achieved by controlling thefluorescence sub-system to emit excitation light for a short period oftime and then detecting the Raman and/or auto-fluorescence spectragenerated from the fiber 107 of the optical probe itself.Advantageously, by using the fluorescence subsystem, the detection andevaluation of optical probe connection can be performed withoutrequiring additional hardware, without using complicated optics(filtering) at the distal end of the catheter, and without putting thecatheter in contact with a patient.

According to at least one embodiment of the present invention, e.g., asillustrated in FIG. 1, the excitation light emitted from excitationsource 810 goes through the optical fiber 107 to the optical probe ofcatheter 160. Raman scattering and/or auto-fluorescence light arespontaneously generated from the fiber 107 itself, in response to thefiber 107 being irradiated with the excitation light emitted fromexcitation source 810. Details of spontaneous Raman scattering and/orauto-fluorescence generation from optical fibers can be found, forexample, in technical documents disclosed by Walrafen et al., “RamanSpectral Characterization of Pure and Doped Fused Silica OpticalFibers”, Applied Spectroscopy, Volume 29, Number 4, 1975, pages 337-344,and Motz et al., “Optical Fiber Probe for Biomedical RamanSpectroscopy”, Applied Optics Vol. 43, No. 3, 20 Jan. 2004. In thepresent disclosure, significant consideration is given to optimizingthroughput and maximizing collection efficiency of the fiber-based Ramanscattering and fluorescence signals. As it is known to those skilled inthe art, the Raman effect allows for only about 1 of every 109excitation photons to produce a Raman signal. For this reason, it isdesirable to collect the fiber-based scattering signal with highsignal-to-noise ratio.

In the system 100 of FIG. 1, the generated Raman scattering and/orauto-fluorescence light are delivered back to the PIU 150, e.g., due toreflection from optical interfaces at the distal end of the fiber. Morespecifically, as illustrated in FIG. 4A, the optical probe 450 shows atleast one interface between fiber 452 and lens 454, and also aninterface between lens 454 and diffracting element 456. These interfacescan cause the return the spontaneously generated Raman and/orauto-fluorescence from the optical probe back towards the fluorescencedetector 122. The Raman scattering and/or auto-fluorescence signal istransmitted to the fluorescence detector 122 via the free-space beamcombiner 300 in the PIU 150. Specifically, as illustrated in FIG. 3A,the beam combiner 300 guides the light from the optical probe channel308 to the return signal channel 304, by passing the generated Ramanscattering and/or auto-fluorescence signal through the optical filters320, such as a long-pass and/or bandpass filter. Then, the Ramanspectrum and/or the fluorescence signal can be detected with aspectrometer and/or the fluorescence detector 122.

In the system 100 shown in FIG. 1, it is also possible to assess theoptical connection of the catheter 160 based on OCT signals detectedfrom a sample. FIGS. 5A through 5C graphically illustrate a comparativeexample of evaluating the optical probe connection based on OCT signalintensity using the system 100 (shown in FIG. 1). To obtain an OCTsignal as shown in FIGS. 5A-5C, the catheter 160 would have to bemechanically connected with PIU 150, and then placed near (insertedinto) a sample 170 (e.g., a bodily lumen). As shown in FIG. 5A, when theoptical probe is optically disconnected from the PIU 150 (e.g., when thefiber 107 is misaligned), even if the OCT light source no is activated,the average a-line profile shows only a signal intensity correspondingto the light source 110 (or system) thermal noise. That is, when theoptical probe is disconnected, there is no sample-based or fiber-basedsignal. However, as shown in FIG. 5B, when the optical probe isconnected to the PIU 150 and the light source 110 is activated, theaverage a-line profile has a signal intensity corresponding to the lightsource (or system) thermal noise and a signal corresponding to OCTsignal returning from the sample 170. In addition, a fiber backgroundsignal (Raman scattering and/or auto-fluorescence spectra) generatedfrom the optical probe fiber itself may be observed. Therefore, as shownin FIG. 5C, the signals obtained when the optical probe is disconnectedand when the optical probe is connected can be used to obtain a signalindicative of whether the optical probe is connected or not.Specifically, FIG. 5C shows the intensity difference by combining(subtracting) the signals detected before and after the optical probe isconnected to PIU 150. However, in order to preform the measurement shownin FIG. 5B, the catheter 160 must be in close contact with an actualsubject (sample 170). In this case, since the fiber's background signalcan be affected by the OCT signal from the sample, the determination ofwhether the optical probe is connected may not be accurate. In addition,this manner of evaluating the optical probe connection is inconvenientbecause a patient would have to be unnecessarily exposed to discomforteven before optical connection is confirmed.

On the other hand, when optical connection is confirmed prior to thecatheter being used in the patient, not only patient's discomfort isavoided but also the optical probe connection is more accuratelymeasured as the OCT signal of the sample will not interfere with thefiber's background signal. FIG. 5C illustrates a graph of the excitationlaser light signal (dashed line), and exemplary Raman and/or autofluorescence spectra (solid line) generated from optical probe fiberitself in response to being irradiated with the excitation laser light.In this manner, as illustrated in FIG. 5C, a return optical signal fromthe fiber 107 which has a wavelength range different from the wavelengthof the excitation light, can be detected independently from theexcitation light using a simplified optical system. Specifically, asshown in FIG. 5C, the Raman and/or auto-fluorescence light generated bythe fiber itself can be accurately separated from excitation light withthe optical filter 320 in the beam combiner 300 of the PIU 150. Theoptical filter 320 can be implemented as a notch filter specificallydesigned to block only a narrow band of wavelengths centered on thewavelength of the excitation light. In this manner, since the wavelengthof the return optical signal is higher than the wavelength of theexcitation signal, the intensity of the return signal will beunobstructed by the optical filter 320. Alternatively, the opticalfilter 320 can be implemented as a band-pass filter specificallydesigned to block wide band of wavelengths lower than the wavelengths ofthe Raman and/or fluorescence light returning from the fiber 107. Inthis manner, since the wavelength of the return optical signal is higherthan the wavelength of the bandpass filter, the intensity of the returnsignal will still be unobstructed by the optical filter 320. Theseparated Raman and/or auto-fluorescence signals unobstructed by theoptical filter 320 and undisturbed by any sample signals can accuratelydetected by the fluorescence detector 122, and then processed bycomputer 190 to determine the optical probe connection status asdescribed in more detail herein below (with reference to FIG. 9).

When the optical probe is disconnected, or not properly aligned with theoptics inside the PIU 150, the signal detected by the fluorescencedetector 122 is very small (almost zero); that detected signalcorresponds to noises such as thermal and/or electrical noise. On theother hand, when the optical probe is properly connected, the signaldetected by the fluorescence detector 122 becomes high.

FIG. 5E illustrates an exemplary detection signal that can be used todetermine whether or not the optical probe 450 of catheter 160 isappropriately connected to the catheter console. As illustrated in FIG.5E, when a detected Raman and/or auto-fluorescence signal is below apredetermined intensity threshold, the optical probe is considered to bein an optically disconnected (OFF) state. Conversely, when a detectedRaman and/or auto-fluorescence signal is equal to or above thepredetermined intensity threshold, the optical probe is considered to bein appropriate optical communication (ON) with the catheter console.

The detector required to produce the signal illustrated in FIG. 5Epreferably senses the return signal of the fiber 107 in a wavelengthrange of about 640 to 900 nm. The wavelength range of the detector isdesigned with either an optical low-pass filter, a high-pass filter, aband-pass filter, or any combination thereof used in the beam combiner300 in the PIU 150, as shown in FIG. 3A. When a spectrometer is usedinstead of the fluorescence detector or in combination with thefluorescence detector, the system is able to obtain not only theintensity, but also the specific spectrum of the return optical signal,so that the system is able to easily differentiate the origin of thespectrum based on the signature spectrum of, for example, materials ofthe core and/or cladding of the fiber 107. The signature spectrum can beused to determine whether the return optical signal is being generatedfrom the optical probe itself or from substances (e.g., biologicalcontaminants or dirt) not appropriate for medical imaging. On the otherhand, when a single detector such as photodiode, avalanche photodiode,or photomultiplier is used as the fluorescence detector 122, thedetection sensitivity becomes high, which is advantageous for detectingeven weak signals Raman scattering and/or fluorescence return signal. Inthis case too, the use of a more sensitive detector can ensure that evenminor failures (misalignment, bending, etc.) of the fiber catheter aremore easily detected.

As shown in FIG. 5D, silica fiber materials pumped with excitation lightof 633 nm can generate a Raman scattering spectrum having multiple peaksat 655, 663, 675 nm (indicated by solid dark arrow pointing down).Therefore, the peak wavelength of one or more of signals at 655, 663,and 675 nm can be used to detect the status of optical probe connection.In this case, an optical detector with narrow band sensitivity maysuffice to detect the optical probe connection. Naturally, it is alsogood to detect the intensity of the return signal in the wavelengthrange from 640 to 700 nm where the Raman signals are high, and thendetermine the optical probe connection based on a statistical analysis(e.g., averaging or integrating) of the signal as a whole. In this case,an optical detector with corresponding broad wavelength sensitivitywould be necessary.

However, since the catheter system can be applicable to many differentuses, the excitation light is not limited to 633 nm. Although the Ramanspectrum of silica fiber materials appears with substantially the sameenergy shifts (530 cm⁻¹, 715 cm⁻¹, 983 cm⁻¹) from the excitation laserwavelength, the excitation wavelength can be changed from 633 nm toother specific wavelengths such as 404, 450, 520, 635, 650, 670, 740,785, 830 nm. Therefore, in the case of changing the excitationwavelength, the detector wavelength range also needs to be changed withthe same energy shift amount as that of the Raman shift. In this regard,it should be noted that excitation wavelengths greater than 830 nm mayneed to use near infrared sensitive detectors.

On the other hand, the auto-fluorescence from the fiber appears high ataround 660 to 720 nm. Therefore, the fluorescence detector 122 alsoneeds to be adjusted to detect the auto-fluorescence at this wavelengthrange of 660 to 720 nm. Theoretically, the auto-fluorescence wavelengthsdo not change even when the excitation wavelength is changed. When theoptical fiber 107 is a double clad fiber (DCF), the Raman scatteringand/or auto-fluorescence signal are efficiently delivered through theclad (cladding) of the DCF so that the detection/collection efficiencybecomes high. The Raman scattering and/or auto-fluorescence signal aregenerated within the optical fiber itself so that this method is notsensitive to catheter sheath materials, distal optics fabricationtolerance, or the length of the optical fiber (most catheters typicallyuse the same fiber length). Therefore, highly reliable detection of theoptical probe connection can be achieved with this method.

<Tissue Auto-Fluorescence>

The specific catheter system 100 illustrated in FIG. 1 is used for,among other things, spectroscopic analysis of bodily lumens, such asblood vessels. To that end, fluorescence sub-system delivers light orother radiation from excitation light source 810 to the distal end ofcatheter 160, where the light exits a catheter window and illuminates anarea near the distal end. With this catheter probe connection, tissueauto-fluorescence can be acquired during measurements. Advantageously,however, the fluorescence signal obtained from the fiber itself duringoptical probe connection detection can be used to more accuratelydetermine the auto-fluorescence spectrum of the tissue being examined.

FIG. 6A is a graph showing an exemplary fiber background spectrum andfluorescence spectra of tissue auto-fluorescence signals. Theauto-fluorescence spectrum and intensity from tissues depends on tissuecharacterizations, for example, the lipid rich plaque (tissue signal 1)has high intensity compared with normal vessel tissue (tissue signal 2),in FIG. 6A. The fiber background of the spectrum shown in FIG. 6A ishigh, but it is relatively constant so that the actual fluorescencetissue signals are calculated by subtracting the fiber background signalthat is acquired before and/or after the actual tissue measurement. Theresult of such subtraction is shown in FIG. 6B. The wavelength range ofauto-fluorescence from the tissue is from approximately 640 nm to 820nm. In this embodiment, fluorescence detector 122 (shown in FIG. 1) is asingle sensor such as photodiode, an avalanche photodiode, aphotomultiplier, or the like, which is configured to detect the fiberbackground signal, tissues signal 1, and the tissue signal 2 (shown inFIG. 6A). The intensity of auto-fluorescence signal is analyzed anddisplayed, by computer 190, for example, as shown in FIG. 6B. Thewavelength range of fluorescence detector 122 can be adjusted, forexample, by using filters, to match with the wavelength range fromapproximately 650 to 810 nm to maximize SNR where it becomes thehighest.

FIG. 7A shows a Signal to Noise Ratio (SNR) from tissue signal 1 aftercorrecting for fiber background noise. Note, the noise is assumed fromshot noise from fiber background noise. FIG. 7B is a graph showingintensity levels of optical probe connection detection and tissuefluorescence measurements as function of time. In FIG. 7B, the intensitylevels of optical probe connection show the exemplary functionality ofcatheter system 100, where at an initial time the probe is in an OFFstate when the Raman and/or auto-fluorescence signal is below a giventhreshold. As time elapses, the probe signal becomes equal to or higherthan the given threshold, and therefore the probe is in an ON state.Thereafter, when catheter system 100 has ensured that the optical probeof the catheter is appropriately connected, the tissue signal 1 (TISSUE1) and tissue signal 2 (TISSUE 2) can be safely and accurately measured.

<OCT and Auto-Fluorescence Measurements>

Imaging of coronary arteries by intravascular OCT and auto-fluorescencecan be achieved with the catheter system 100 described in the embodimentof FIG. 1. The system can be used, for example, to see vessels (e.g.,coronary artery) to diagnose stenosis regions and high-risk plaquepresence. In addition, the system 100 has a particular feature to detectand/or monitor connection of catheter probes by using Raman and/orauto-fluorescence signals acquired from the optical fiber itself beforethe catheter is applied to the patient. With this feature, the cathetersystem 100 is able to take measures to prevent from secondary harms, andnotify users of potential errors when the catheter probe is not yetconnected or becomes un-expectedly disconnected. The process ofdetecting and evaluating the status of the optical probe connection tothe catheter console is described in S902-S910 of FIG. 9. However,ensuring appropriate optical probe connection to the catheter console isonly part of the function of the multi-modality system 100 describedherein. As previously mentioned, the system 100 is applicable forimaging of coronary arteries and other similar imaging applicationswhere catheters and/or endoscopes are necessary.

<System Control and Image Processing>

FIG. 8A illustrates an exemplary implementation of an electronic systemconsole 800 connected to the multimodality catheter 160. FIG. 8B is afunctional block diagram of an exemplary computer control system forperforming control and image processing in the multimodality cathetersystem. A system console 800 to acquire multi-modality images using thecatheter 160 is shown in the diagram of FIG. 8A. The system console 800includes or is connected to, for example, an OCT modality 820, theexcitation light source 810, a detector 840, spectrometer 830, a patientinterface unit (PIU) 150, and computer 190. The system console 800 isconnected to the PIU 150 via one or more cables (a cable bundle 835).The optical catheter 160 has a proximal end attachable to the PIU 150and a distal end thereof configured to house therein the optical probewhich is used to illuminate an area of a sample located at a workingdistance from the distal end.

Similar to FIG. 1, the OCT modality 820 in FIG. 8A can include aninterferometer and a tunable laser source or a lamp that outputs lightof broadband spectrum in the infrared range of about 1250 to 1350 nm.The excitation light source 810 can be a laser or an LED that outputslight of a single color (single wavelength) or a narrow band spectrum.The range of the wavelength of the excitation light source 810 can bewithin the visible region, which is from about 400 nm thorough 800 nm.However, other wavelengths in the near-infrared range may also be used.In the exemplary system console Boo, OCT light can be directly guided orotherwise coupled into an OCT source fiber 833; the excitation lightfrom excitation light source 810 can be similarly directly guided orotherwise proved into an excitation source fiber 832. The light from theOCT light source and from the excitation light source are transferred tothe optical catheter 160 by the optics of the beam combiner 300 arrangedwithin the PIU 150.

The catheter 160 is connected at its proximal end thereof to the PIU 150via the catheter connector 180. The catheter 160 includes the fiber 107and an assembly of distal optics (optical probe described above)arranged within the distal end of the catheter. In this manner,illumination light emitted from OCT light source of the OCT modality 820and excitation light from light source 810 can be delivered to thedistal optics of catheter 160, and then directed by a diffractingelement (grating) or reflecting element (mirror) onto an area of sample170. The light scattered back from an area of the target sample (e.g.,tissue) can be collected by the cladding of fiber 107, or by detectingfibers arranged around the distal end of optical probe (see FIGS.10A-10B). The collected light is guided back to the PIU 150 by thecladding of fiber 107, or the one or more detection fibers other thanthe fiber 107. In the PIU 150, the beam combiner 300 selectively guidesthe measurement results (fluorescence and OCT scattered light) to one ormore of detectors 121 and 122.

For detection of optical probe connection, as described elsewhere inthis specification, the catheter 160 is preferably not yet poisonedwithin a patient. Therefore, during detection of the optical probeconnection, light from a target sample is not collected. Instead, theexcitation light is activated for a short period of time to illuminatethe fiber inside the catheter 160, whereby the materials of the coreand/or cladding of the fiber undergo a process of Raman scatteringand/or fluorescence emission. The Raman scattering and/or fluorescencelight generated from the fiber 107 returns to the console and isdetected by the detector/spectrometer 830. Since fiber output from thefiber 831 is dispersive, the fiber connector is placed closely near thedetector, or a collimating/dispersing optical system 834 is used.Specifically, the Raman scattering and/or fluorescence light returnedfrom the fiber 107 is guided by a fiber 831 from the PIU 150 tospectrometer/detector 830. In this manner, the intensity of the Ramanand/or fluorescence signal returned from the fiber and optical probe, orthe intensity of a selected wavelength can be accurately detectedwithout being distorted by fluorescence or scattering from the sample.The function of detecting a selected wavelength of return optical signalcan be performed by selecting a specific single wavelength or a specificwavelength range with the spectrometer or optical filters.

During actual medical imaging, by mechanically rotating the opticalprobe of catheter 160 with the FORJ, it is possible to obtaintwo-dimensional images of the target sample. On the other hand, duringdetection of optical probe connection, rotation of the optical probe canbe avoided as long as a return optical signal including Raman and/offluorescence spectra can be obtained. Computer 190 includes one or moremicroprocessors configured to control and operate the various parts ofsystem console 800 by executing computer-executable instructions(program code). Computer 190 can also be programmed to evaluate thestatus of optical probe connection based on the return optical signaland to reconstruct images of a sample based on signals obtained fromirradiating the sample.

FIG. 8B is a schematic functional diagram of exemplary computer hardwareused to control for the multi-modality catheter system console 800 (and100 in FIG. 1). As shown in FIG. 8B, the computer 190 includes a centralprocessing unit (CPU) 891, a storage memory (ROM/RAM) 892, a userinput/output (I/O) interface 893, and a system interface 894. Thevarious components of the computer 190 communicate with each other viaphysical and logical data lines (DATA BUS).

Storage memory 892 includes one or more computer-readable and/orwritable media, and may include, for example, a magnetic disc (e.g., ahard disk drive HHD), an optical disc (e.g., a DVD®, a Blu-ray®, or theline), a magneto-optical disk, semiconductor memory (e.g., anon-volatile memory card, Flash® memory, a solid state drive, SRAM,DRAM), an EPROM, an EEPROM, etc. Storage memory 892 may storecomputer-readable data and/or computer-executable instructions includingOperating System (OS) programs, and control and processing programs.

The user interface 893 provides a communication interface (electronicconnections) to input/output (I/O) devices, which may include akeyboard, a display (LCD or CRT), a mouse, a printing device, a touchscreen, a light pen, an external optical storage device, a scanner, amicrophone, a camera, a drive, communication cable and a network (eitherwired or wireless).

The system interface 894 also provides an electronic interface(electronic connection circuits) for one or more of the OCT light source110, excitation light source 810, detector/spectrometer 830 (in FIG. 8A)or the detector 121 and detector 122 (in FIG. 1), data acquisitionelectronics DAQ1 (131) and DAQ (132), and the patient unit interface(PIU) 150. The system interface 894 may include programmable logic foruse with a programmable logic device (PDL), such as a Field ProgrammableGate Array (FPGA) or other PLD, discrete components, integratedcircuitry (e.g., an Application Specific Integrated Circuit (ASIC)), orany other components including any combination thereof.

The function of the user interface 893 and of the system interface 894may be realized at least in part by computer executable instructions(e.g., one or more programs) recorded in storage memory 892 and executedby CPU 891. Moreover, the computer 190 may comprise one or moreadditional devices, for example, components such as a communications ornetwork interface for communicating with other medical devices, such asa Picture archiving and communication system (PACS).

<Catheter Connect and Disconnect Process>

FIG. 9 shows an exemplary process (method) for catheter connection,sample measurement, and catheter disconnection. The process is performedbased on the structure of the system described above with reference toFIG. 1. According to this process, the catheter system 100 becomes morereliable by adding detection and/or monitoring of optical probeconnection at several steps of the process. Also, this process preventsfrom performing erroneous operations and from damage to the PIU andcatheters.

In operation, as shown in FIG. 9, catheter connection is required at thebeginning (START) of the process. The catheter handle is mechanicallyconnected to the PIU by users. So catheter and the console are attachedto each other at step 902. Specifically, at step S902 catheter handleconnection occurs when a user manually connects the proximal end ofcatheter 160 to the PIU 150 (console). Once the catheter is connected,the connection is detected with a sensor such as touch sensors, opticalsensors, and/or pressure sensors (not shown). The mechanical connectiondetected by a sensor is converted to an electrical signal, and then theelectrical signal is transferred to the console of the system torecognize the catheter handle connection by executing softwareinstructions with the CPU of computer 190.

Specifically, at step S904, the CPU of computer 190 runs a macro whichconfirms whether or not the catheter has been mechanically connected tothe console. In the case that the CPU of computer 190 confirms that acatheter has been mechanically connected to the console, the processadvances to step S9O6. In the event that the CPU of computer 190 cannotconfirm that a catheter is connected to the console, the process entersa loop of steps S902 to S904 until a user actively connects a catheterto the PIU 150. In this loop, the console of catheter system 100 mayissue a warning or prompt informing the user that a catheter has notbeen detected.

Evaluation of optical probe connection. At step S906, after a catheterhas been determined to be connected to the console, but prior to usingthe catheter in a patient, the CPU of computer 190 controls the systemto detect and evaluate an optical signal (a return optical signal) fromthe catheter. To that end, for example, the CPU of computer 190 controlsthe excitation light source 810 to emit a beam of excitation light, andthen controls the fluorescence detector 122 to detected a signalreturning from the fiber 107 of catheter 160.

For evaluation of the probe connection, when the signal of thefluorescence detector 122 crosses a certain threshold, the computer 190judges the probe connections. At step S908, after activating the lightsource 810 and controlling the fluorescence detector 122 to detect areturn signal, the CPU of computer 190 determines whether the signaloutput by detector 122 is greater than a predetermined threshold (TH1).If the return signal detected is greater than the threshold, the CPUdetermines that the optical probe is properly connected to the console,and the process proceeds to actual imaging measurement process (standby,live view, and recording mode). In the event that the return signaldetected by fluorescence detector 122 is not greater than the threshold,the CPU determines that the optical probe is not properly connected tothe console, and the process proceeds to S910.

Generally, when the catheter is mechanically connected to the console,the optical probe is automatically engaged to the PIU. However, whenautomatic engagement does not occur, at step S910, the CPU of computer190 prompts the user to actively re-engage the optical probe to theconsole. For example, the CPU of computer 190 issues a visual or auralindication that the optical probe is not yet connected (or it is notproperly connected), and requests the user to, for example, manuallyremove and reconnect the catheter 160 to the PIU 150. This event canoccur, for example, in the case where the fiber or optical probe of thecatheter 160 is broken or bent, or otherwise not able to transmit enoughlight therethrough. The system may ask users to operate the catheter tore-engage the optical probe and/or stop the probe engagement process toreplace the damaged probe with new catheter. For evaluation of the probeconnection, when the signal of the fluorescence detector 122 crossesthreshold (TH1), the CPU of computer 190 judges the probe connection isappropriate. The loop of steps S906, S908 and S910 is repeatedlyperformed until the CPU of computer 190 makes a determination that areturn optical signal detected by fluorescence detector 122 is above thepredetermined threshold value (YES in step S908).

After the system confirms that the optical probe is successfully engagedand optically aligned, the system is ready for imaging, or it moves to astandby mode to wait for a measurement command. In an actual imagingoperation, there are a standby mode (S912), a live view mode (S914), anda recording mode (S916), which are typical modes of a catheter system.In the standby mode, the catheter system stops any lasers and motors sothe system does not generate any images, but simply waits for a user'scommand. In the live view mode, the system is actively imaging to showreal-time (live view) images, e.g., during navigation of the cathetertowards a region of interest, but does not record the live view images.In the recording mode, the system is fully operational to activelyacquire and record images of a desired target location.

At step S918, the system is programed to prompt the user whether animaging operation should continue or not. In the event that imagingshould not continue (NO in S918), the system advances to step S920 andbegins optical probe disengagement. Specifically, in step S920, theoptical probe is automatically disengaged from the PIU 150 once a usersends a command to the console to eject the catheter. The optical fiberconnector of the optical probe will be disconnected in this mode.Subsequently, at step S922, the system evaluates the optical signaldetected by fluorescence detector 122; and at step S924 computer 190 ofthe system performs an evaluation of optical probe connection based onthe signal detected by fluorescence detector 122.

Specifically at step S924, the system confirms that the optical probe issuccessfully disengaged (Probe disconnected), if the signal at thefluorescence detector 122 is less than a predetermined disconnectionthreshold (TH2). Otherwise if the signal detected at fluorescencedetector 122 is still greater than the disconnection threshold (TH2),the system goes back to the optical probe disengagement step S920. Inthis step S920, the system may prompt users to operate probedisengagement. For evaluation of the probe connection, when the signaldetected by the fluorescence detector 122 is below (crosses) thedisconnection threshold (TH2), the computer 190 judges that the opticalprobe is disconnected. In this case, the process advances to step S926,where the system may issue a prompt to the user to mechanicallydisconnect the catheter from the system. Therefore, the loop of S920,S922 and S924 can be repeated until the system determines that theoptical probe has been disconnected from the console and the signals ofthe fluorescence detector 122 are lower than the threshold (TH2).

After determining that the optical probe is disconnected, at step S926,the system may prompt users to remove catheter handle from the connector180. Catheter handle disconnect occurs when the catheter handle ismechanically disconnected from the PIU 150 by users. Once the catheteris manually detached from the console the process can end or a newcatheter can be mechanically attached.

In the flow process of FIG. 9, the threshold TH1 and the threshold TH2can be established, for example, as a percentage of the expectedintensity of the Raman scattering and/or fluorescence signal generatedfrom the fiber itself. The expected intensity of the Raman scatteringand/or fluorescence signal of the fiber may be obtained from the fiber'smanufacturer, or may be obtained by experimental measurement. In afiber-optic-based catheter, as described above, one or more lightconducting fibers can be used to transmit light in both directions(illumination and collection). Propagation of light along optical fibersoccurs because of the effect known as total internal reflection.Nevertheless, various loss-producing mechanisms such as launch couplingloss, fiber attenuation, splice losses, and connector losses reduce theintensity of the light transmitted from one end to the other of thecatheter. In this regard, the general principles of the optical powerbudget for a fiber-optic communication link may be used to determine theexpected intensity to be received by the fluoresce detector 122.

For example, in one embodiment, the threshold TH1 or the threshold TH2can be determined based on the optical power P (e.g., 0 dBm=1 mW) of theexcitation light source, the expected thermal noise N_(th) of thedetector, and any possible optical losses η due to fiber dispersion,connector losses, cross-talk, etc. In that case, the threshold TH1 fordetermining of whether the optical probe has been properly connected tothe console at S908 can be, for example, 75% or higher than theintensity of the florescence signal expected to be received at thefluorescence detector 122. In this manner, a low signal (e.g., 30% ofexpected intensity) due to misalignment of the fiber connector or due tocontamination (dirt or dust) in the fiber connection would prompt theuser to review the connection or to change the catheter. On the otherhand, the threshold TH2 for determining whether the optical probe hasbeen fully disconnected from the console at step S924 can be, forexample, 10% or lower than the intensity of the fluorescence signalexpected to be received at the fluorescence detector 122. In thismanner, the user can ensure that the optical probe is completeddisengaged and that any signal present at the fluorescence detector 122is only due to thermal or spurious noise. In other embodiments, thethreshold TH1 and the threshold TH2 can be set to a similar value, forexample, as a percentage (e.g., 50%) of the expected intensity of thefluoresce signal. In this case, when the signal at S908 is equal to orgreater than TH1, the system can determine that the optical probe of thecatheter is properly connected to the console. And conversely, when thesignal at S924 is below TH2 (where TH2≈TH1), the system can determinethat the optical probe of the catheter is disconnected from the console.

As described above, the catheter may include a single double-clad fiber(DCF) for delivering and collecting light to and from the sample.However, the catheter can be modified to include a fiber having morethan two claddings (a multi-cladding fiber), or a fiber bundle, or aholey fiber (a photonic crystal microstructure fiber), or a custom-mademulti-fiber structure, or combinations thereof. Furthermore, thecatheter may be replaced by an endoscope having the optical probe formedof a bundle of one or more optical fibers. FIG. 10A shows across-sectional view of an exemplary fiber bundle, and FIG. 10B shows amulti-fiber structure. In both FIGS. 10A and 10B, a center fiber isfiber 107 used for delivering and collecting the OCT signal, while theplurality of fibers (Fiber 1, Fiber 2, Fiber 3 . . . , Fiber n)surrounding the center fiber are either multimode fibers (MMF) or singlemode fibers used for collecting the backscattered and fluorescence lightfrom the sample.

While the present patent application has been described with referenceto exemplary embodiments, it is to be understood that the invention isnot limited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all possible modifications and equivalent structures andfunctions. To that end, it must be noted that the terminology usedherein is for the purpose of describing particular embodiments only andis not intended to be limiting.

It should be further noted that operations performed as methodsteps/processes or otherwise described herein in algorithm form arethose operations requiring physical manipulations of physicalquantities, which usually but not necessarily, take the form ofelectrical or magnetic signals capable of being stored, transferred,combined, transformed, compared, and otherwise manipulatedelectronically. Therefore, unless specifically stated otherwise, it willbe apparent to those skilled in the art that throughout the abovedescription, discussions utilizing terms such as “processing” or“computing” or “displaying” or “calculating” or “comparing,“calibrating” “generating” or “determining” and the like, refer to theaction and processes of a computer system, or similar electroniccomponent, that manipulates and transforms data represented as physical(electronic) quantities within the computer system's registers andmemories into other data similarly represented as physical quantitieswithin the computer system memories or registers or other suchinformation storage, transmission, or display device.

<Other Definitions>

Unless defined otherwise herein, all technical and scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which this invention belongs. The breadth of thepresent invention is not to be limited by the subject specification, butrather only by the plain meaning of the claim terms employed.

It should be understood that if an element or part is referred herein asbeing “on”, “against”, “connected to”, or “coupled to” another elementor part, then it can be directly on, against, connected or coupled tothe other element or part, or intervening elements or parts may bepresent. In contrast, if an element is referred to as being “directlyon”, “directly connected to”, or “directly coupled to” another elementor part, then there are no intervening elements or parts present. Whenused, term “and/or”, may be abbreviated as “/”, and it includes any andall combinations of one or more of the associated listed items, if soprovided.

Spatially relative terms, such as “under” “beneath”, “below”, “lower”,“above”, “upper”, “proximal”, “distal”, and the like, may be used hereinfor ease of description to describe one element or feature'srelationship to another element(s) or feature(s) as illustrated in thevarious figures. It should be understood, however, that the spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. For example, if the device in the figures is turned over,elements described as “below” or “beneath” other elements or featureswould then be oriented “above” the other elements or features. Thus, arelative spatial term such as “below” can encompass both an orientationof above and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein are to be interpreted accordingly. Similarly, the relativespatial terms “proximal” and “distal” may also be interchangeable, whereapplicable.

The term “about” or “approximately” as used herein means, for example,within 10%, within 5%, or less. In some embodiments, the term “about”may mean within measurement error. In this regard, where described orclaimed, all numbers may be read as if prefaced by the word “about” or“approximately,” even if the term does not expressly appear. The phrase“about” or “approximately” may be used when describing magnitude and/orposition to indicate that the value and/or position described is withina reasonable expected range of values and/or positions. For example, anumeric value may have a value that is +/−0.1% of the stated value (orrange of values), +/−1% of the stated value (or range of values), +/−2%of the stated value (or range of values), +/−5% of the stated value (orrange of values), +/−10% of the stated value (or range of values), etc.Any numerical range, if recited herein, is intended to include allsub-ranges subsumed therein.

The terms first, second, third, etc. may be used herein to describevarious elements, components, regions, parts and/or sections. It shouldbe understood that these elements, components, regions, parts and/orsections should not be limited by these terms. These terms have beenused only to distinguish one element, component, region, part, orsection from another region, part, or section. Thus, a first element,component, region, part, or section discussed below could be termed asecond element, component, region, part, or section without departingfrom the teachings herein.

In describing example embodiments illustrated in the drawings, specificterminology is employed for the sake of clarity. However, the disclosureof this patent specification is not intended to be limited to thespecific terminology so selected and it is to be understood that eachspecific element includes all technical equivalents that operate in asimilar manner.

While the present disclosure has been described with reference toexemplary embodiments, it is to be understood that the presentdisclosure is not limited to the disclosed exemplary embodiments. Thescope of the following claims is to be accorded the broadestinterpretation so as to encompass all such modifications and equivalentstructures and functions.

LIST OF EXEMPLARY REFERENCES

The following non-patent literature (NPL) and patent publications, whichare considered “nonessential material”, are hereby incorporated byreference herein in their entirety:

-   -   1. Motz et al., “Optical Fiber Probe for Biomedical Raman        Spectroscopy”, Applied Optics Vol. 43, No. 3, 20 Jan. 2004;    -   2. Ma et al., in “Fiber Raman background study and its        application in setting up optical fiber Raman probes”, Appl.        Opt. 1996;    -   3. Walrafen et al., in “Raman Spectral Characterization of Pure        and Doped Fused Silica Optical Fibers”, Applied Spectroscopy,        Volume 29, Number 4, 1975, pages 337-344.    -   4. Patent publications include: U.S. Pat. No. 8,758,223,        6,009,220, 5,625,450, 7,132,645, and 6,069,691; and pre-grant        publications (PGPUB) US 2008/0304074 (Brennan), US 2012/0176613        (Marple et al.), and US 2003/0077043 (Hamm et al.).

What is claimed is:
 1. A catheter system, comprising: an electronicconsole; an excitation light source configured to emit excitationradiation; a catheter having a proximal end attachable to the consoleand a distal end configured to house therein an optical probe; anoptical fiber configured to transmit from the console to the opticalprobe excitation radiation emitted from the excitation light source, andconfigured to collect an optical response signal having a wavelengthlonger than that of excitation radiation; a detector configured todetect intensity or wavelength of the optical response signal; and aprocessor configured to determine, based on the detected intensity orwavelength, whether the optical probe is properly connected to theconsole, wherein the optical response signal is generated by at leastone of photon scattering and auto-fluorescence within the optical fiberitself in response to transmitting the excitation radiationtherethrough.
 2. The catheter system according to claim 1, wherein theoptical fiber is a double clad fiber comprising a core concentric withthe longitudinal axis of the optical fiber, an inner claddingsurrounding the core, and an outer cladding surrounding the innercladding.
 3. The catheter system according to claim 2, wherein theoptical response signal is an auto-fluorescence signal generated fromdopant materials used to form the inner and/or the outer cladding of theoptical fiber, the auto-fluorescence signal being generated in responseto transmitting the excitation radiation through the inner and/or theouter cladding of the optical fiber.
 4. The catheter system according toclaim 1, wherein the optical response signal is a Raman scatteringsignal generated from the optical fiber itself in response totransmitting the excitation radiation therethrough.
 5. The cathetersystem according to claim 4, wherein the optical fiber is a double cladfiber comprising a core concentric with the longitudinal axis of theoptical fiber, an inner cladding surrounding the core, and an outercladding surrounding the inner cladding, and wherein the Ramanscattering signal is generated from silica material used to form thecore of the optical fiber, the Raman scattering being generated inresponse to transmitting the excitation radiation through the core ofthe optical fiber.
 6. The catheter system according to claim 1, whereinthe optical fiber is a double clad fiber having a central longitudinalaxis extending from the proximal end to the distal end of the catheter,the double clad fiber comprising a core concentric with the longitudinalaxis, an inner cladding surrounding the core, and an outer claddingsurrounding the inner cladding.
 7. The catheter system according toclaim 1, further comprising a laser source configured to emit theexcitation radiation, wherein the wavelength of the excitation radiationis in the range of about 400 to 800 nm.
 8. The catheter system accordingto claim 1, wherein processor determines whether the optical probe isproperly connected to the console by analyzing the detected opticalreturn signal at a specific wavelength range.
 9. The catheter systemaccording to claim 1, wherein processor determines whether the opticalprobe is properly connected to the console by analyzing the detectedoptical return signal at a specific wavelength.
 10. The catheter systemaccording to claim 1, further comprising a free-space beam combinerconfigured to separate the excitation light from the return opticalsignal, wherein the free-space beam combiner includes one or moreoptical filters configured to block the excitation light from beingreturned to the detector.
 11. The catheter system according to claim 1,further comprising a radiation source different from the excitationsource, wherein the optical response signal is generated as a functionof auto-fluorescence or Raman scattering of the optical fiber itself inresponse to transmitting the excitation radiation therethrough, whereinthe radiation source emits a radiation of first wavelength, and theradiation of first wavelength emitted from the radiation source iscoupled into the optical probe via the optical fiber, and radiation of asecond wavelength is collected by the optical probe from an areasurrounding a distal end of the optical probe, and wherein the processorcontrols the radiation source to emit the radiation of first wavelengthbased on a determination of whether the optical probe is properlyconnected to the console.
 12. The catheter system according to claim 1,further comprising; a patient interface unit (PIU) operatively connectedto the proximal end of the catheter, wherein the PIU includes a fiberoptic rotary joint (FORJ), a rotational motor and translation stage,wherein the optical fiber is a double clad fiber disposed in aprotective sheath, wherein the FORJ is configured to provideuninterrupted transmission of the excitation radiation having a firstwavelength and OCT radiation having a second wavelength from one or morelight sources other than the excitation light source, and wherein theFORJ is configured to provide uninterrupted transmission of collectedradiation to the detector while rotating the double clad fiber withinthe catheter during a pullback operation.
 13. A method of determiningoptical connection of a catheter to an electronic console, the catheterhaving a proximal end attachable to the console, a distal end configuredto house therein an optical probe, and an optical fiber that extendsfrom the distal end to the optical probe, the method comprising:connecting the proximal end of the catheter to the console; transmittingexcitation radiation from an optical source to the optical probe throughthe optical fiber, and collecting an optical response signal having awavelength longer than that of excitation radiation; detecting theintensity or wavelength of the optical response signal; and determining,based on the detected intensity or wavelength, whether the optical probeof the catheter is properly connected to the console, wherein theoptical response signal is generated by at least one of photonscattering and auto-fluorescence within the optical fiber itself inresponse to transmitting the excitation radiation therethrough.
 14. Themethod according to claim 13, wherein the optical fiber is a double cladfiber comprising a core concentric with the longitudinal axis of thefiber, an inner cladding surrounding the core, and an outer claddingsurrounding the inner cladding.
 15. The method according to claim 14,wherein the optical response signal is an auto-fluorescence signalgenerated from dopant materials used to form the inner and/or the outercladding of the fiber, the auto-fluorescence signal being generated inresponse to transmitting the excitation radiation through the innerand/or the outer cladding of the optical fiber.
 16. The method accordingto claim 13, wherein the optical response signal is a Raman scatteringsignal generated from the optical fiber itself in response totransmitting the excitation radiation therethrough.
 17. The methodaccording to claim 16, wherein the optical fiber is a double clad fibercomprising a core concentric with the longitudinal axis of the fiber, aninner cladding surrounding the core, and an outer cladding surroundingthe inner cladding, and wherein the Raman scattering signal is generatedfrom silica material used to form the core of the optical fiber, theRaman scattering signal being generated in response to transmitting theexcitation radiation through the core of the optical fiber.
 18. Themethod according to claim 13, wherein the step of transmittingexcitation radiation through the optical fiber includes emitting theexcitation radiation in a wavelength range of about 400 nm to 800 nm.19. The method according to claim 13, wherein the step of determiningwhether the optical probe is properly connected to the console includesanalyzing the detected optical return signal at a specific wavelengthrange.
 20. The method according to claim 13, wherein the step ofdetermining whether the optical probe is properly connected to theconsole includes analyzing the detected optical return signal at aspecific wavelength.
 21. The method according to claim 13, furthercomprising: separating the excitation light from the return opticalsignal using a free-space beam combiner, wherein the free-space beamcombiner includes one or more optical filters configured to block theexcitation light for being returned from the optical fiber to theconsole; and detecting the return optical signal without detectingexcitation light.
 22. The method according to claim 13, furthercomprising: emitting OCT radiation different from the excitationradiation, in response to determining that the optical probe of thecatheter is properly connected to the console.
 23. The method accordingto claim 13, wherein the step of determining whether the optical probeof the catheter is properly connected to the console includesdetermining whether the detected intensity of the optical return signalis higher than a predetermined threshold value.
 24. An apparatus fortesting whether an optical probe is properly connected to a device,comprising: a laser source configured to output an excitation beam; anoptical fiber configured to transmit the excitation beam from the lasersource to the optical probe, and configured to collect an opticalresponse signal generated from the optical fiber itself; a detectorconfigured to detect intensity or wavelength of the optical responsesignal; and a processor configured to determine, based on the detectedintensity or wavelength, whether the optical probe is properly connectedto the device, wherein the optical response signal is generated by atleast one of photon scattering and auto-fluorescence within the opticalfiber itself in response to transmitting the excitation beamtherethrough, and wherein the optical response signal has a wavelengthlonger than that of the excitation beam.
 25. The apparatus according toclaim 24, further comprising: an OCT light source configured to outputan irradiation beam; wherein the optical fiber transmits the irradiationbeam from the OCT light source to the optical probe, and the opticalprobe directs the irradiation beam onto a sample, in response to theprocessor determining that the optical probe is properly connected tothe device.